1. Field of the Invention
The present invention relates to a technique for directing light onto various substrates including a semiconductor substrate, a printed circuit board, a substrate for a color filter provided in a liquid crystal display device and the like, a glass substrate for a flat panel display provided in a liquid crystal display device, a plasma display device and the like, a substrate for a magnetic disk, a substrate for an optical disk, a solar cell panel and the like (hereinafter referred to simply as “substrates”) to draw patterns on the substrates.
2. Description of the Background Art
For the process of exposing a photosensitive material applied onto a substrate to light to form a circuit pattern and the like, attention has been given in recent years to an exposure apparatus (what is called a drawing apparatus) which does not use a mask but scans the photosensitive material applied onto the substrate with light (a beam of drawing light) modulated in accordance with data including descriptions of the pattern to directly expose the photosensitive material with the light, thereby forming the pattern. The drawing apparatus includes an optical head having, for example, a spatial light modulator for modulating a light beam on and off on a pixel-by-pixel basis (e.g., a reflective spatial modulator which uses a control signal to switch between an on state in which a light beam supplied from a light source is reflected onto a substrate and an off state in which a light beam is reflected in a direction different from that in the on state on a pixel-by-pixel basis). The drawing apparatus directs a drawing light beam from the optical head onto a substrate moved relative to the optical head to expose the substrate to the drawing light beam, thereby forming a pattern (or to draw a pattern on the substrate), as disclosed in Japanese Patent Application Laid-Open No. 2009-237917, for example.
While emitting the drawing light beam, for example, of a strip-shaped cross-sectional configuration, the optical head in the drawing apparatus moves relative to the substrate along an axis (main scanning axis) orthogonal to the direction of the longer dimension of the strip-shaped cross section of the drawing light beam (which is referred to as a main scanning process). This main scanning process causes the exposure to light to form a pattern corresponding to a single strip-shaped region extending along the main scanning axis on the substrate. Upon completion of the main scanning process involving the emission of the drawing light beam, the optical head subsequently moves relative to the substrate along a sub-scanning axis orthogonal to the main scanning axis, and then performs a main scanning process involving the emission of the drawing light beam again. This causes the exposure to light to form a pattern corresponding to a strip-shaped region adjacent to the strip-shaped region subjected to the pattern exposure by the preceding main scanning process. In this manner, the main scanning process involving the emission of the drawing light beam is performed repeatedly, with the sub-scanning process performed between adjacent main scanning processes, whereby the entire region of the substrate is subjected to the pattern exposure.
In the process of exposing a substrate to light to form a pattern by the aforementioned method, there has been a problem such that nonuniformity of light exposure is prone to occur in boundary sections between the strip-shaped regions. There is a possibility that the nonuniformity of light exposure in the boundary sections causes discontinuity of the pattern (e.g., a break in the pattern, and the increase and decrease in the thickness of the pattern) in the boundary sections and the like. The discontinuity of the pattern might exert adverse effects on the electrical characteristics (current-carrying characteristics) of finished products.
To solve such a problem, Japanese Patent Application Laid-Open No. 2008-129248 discloses a technique in which the distance of movement in the sub-scanning direction is made shorter than the longer dimension of the strip-shaped cross section of the light beam emitted from the optical head, so that the boundary sections of the strip-shaped regions overlap each other. This configuration causes the influences of the nonuniform characteristics of the optical head to be mixed and made uniform, thereby reducing the nonuniformity of light exposure in the boundary sections between the strip-shaped regions.
The use of the technique disclosed in Japanese Patent Application Laid-Open No. 2008-129248 reduces the nonuniformity of light exposure in the boundary sections between the strip-shaped regions to some extent. However, how the nonuniformity of light exposure appears in the boundary sections between the strip-shaped regions varies significantly depending on processing conditions.
Specifically, the boundary sections are sections in which regions irradiated with light at different times are adjacent to each other (or overlap each other). For this reason, how the nonuniformity of light exposure appears in the boundary sections varies, for example, with changes in the type of a photosensitive material, in optical diffusion characteristics and the like. As the speed of movement of the optical head relative to the substrate, for example, is varied, a difference in timing of the irradiation of the boundary sections with light is varied, so that how the nonuniformity of light exposure appears is accordingly varied.
There is hence a great likelihood that even a slight change in processing conditions causes the nonuniformity of light exposure in the boundary sections to occur although appropriate adjustments are made under certain processing conditions so that the nonuniformity of light exposure in the boundary sections does not occur. Thus, a change in processing conditions requires an immediate adjustment to be made again. However, this adjustment is not easily made conventionally. The conventional techniques cannot flexibly respond to changes in processing conditions to have difficulties in sufficiently ensuring the uniformity of light exposure.